# The Energy Efficiency Ratio (EER)

The Energy Efficiency Ratio (EER) of an HVAC cooling device is the ratio of output cooling energy (in BTU) to input electrical energy (in watts) at a given operating point. EER is normally calculated with a 95 °F outside temperature and an inside (return air) temperature of 80 °F and 50% relative humidity.

Similarly, The Seasonal Energy Efficiency Ratio (SEER) rating of a unit looks at an air conditioner a bit more granularly—calculating the cooling capacity during a typical cooling-season (rather than all-time) divided by the total electric input during the same period.

Example:

For example, consider a 5000 BTU/h (1465-watt cooling capacity) air-conditioning unit, with a SEER of 10 BTU/(W·h), operating for a total of 1000 hours during an annual cooling season (e.g., 8 hours per day for 125 days).

The annual total cooling output would be:

5000 BTU/h × 8 h/day × 125 days/year = 5,000,000 BTU/year

With a SEER of 10 BTU/(W·h), the annual electrical energy usage would be about:

5,000,000 BTU/year ÷ 10 BTU/(W·h) = 500,000 W·h/year

The average power usage may also be calculated more simply by:

Average power = (BTU/h) ÷ (SEER) = 5000 ÷ 10 = 500 W = 0.5 kW

If your electricity cost is \$0.20/(kW·h), then your cost per operating hour is:

0.5 kW × \$0.20/(kW·h) = \$0.10/h

The efficiency of air conditioners is often rated by the seasonal energy efficiency ratio (SEER) which is defined by the Air Conditioning, Heating, and Refrigeration Institute in its 2008 standard AHRI 210/240, Performance Rating of Unitary Air-Conditioning and Air-Source Heat Pump Equipment. A similar standard is the European seasonal energy efficiency ratio (ESEER).

The SEER rating of a unit is the cooling output during a typical cooling-season divided by the total electric energy input during the same period. The higher the unit’s SEER rating the more energy efficient it is. In the U.S., the SEER is the ratio of cooling in British thermal units (BTUs) to the energy consumed in watt-hours. The coefficient of performance (COP), a more universal unit-less measure of efficiency.

Dragon Air Services is a family-owned business located in the heart of Plano. We specialize in residential Air Conditioning and Heating repairs, Air Conditioning, and Heating replacements, and Air conditioning and Heating service. Our expert technicians pride themselves on providing honest diagnostics so our customers can make educated decisions on what’s best for them. If you are in need of replacing an HVAC unit in Dallas, Plano or surrounding cities call us today at 214-790-9872 to schedule an appointment.

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